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United States Department of Agriculture

Agricultural Research Service

Research Project: Improvement of Prunus and Vitis Scions for Fruit Quality and Pest Resistance Title: Progress in Breeding Powdery Mildew Resistant Table Grapes and a Brief Description of ‘Valley Pearl'

Author
item Ramming, David

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 20, 2012
Publication Date: February 21, 2012
Citation: Ramming, D.W. 2012. Progress in Breeding Powdery Mildew Resistant Table Grapes and a Brief Description of ‘Valley Pearl'. San Joaquin Valley Table Grape Seminar. p. 41-43.

Interpretive Summary: Powdery mildew is the single most important fungal disease of grapes in the world. All currently available table grapes grown in California are susceptible and cannot be grown without sprays to control this disease. Resistant germplasm has been selected by researchers from many different sources and is being used in a breeding program in Parlier, CA to develop seedless table grapes with resistance to powdery mildew. Molecular markers are available to aid in combining several sources of resistance into one plant. In 2011, 20 table grape seedlings were selected based on resistance and good fruit quality. One red seedless selection will be tested in a 27 vine production plot. A white resistant selection will fruit in a 27 vine production plot in 2012 and has very good eating quality, small aborted seeds and good production. This powdery mildew resistant table grape material will provide growers with table grape cultivars that do not need to be sprayed for powdery mildew. Valley Pearl, a new early to mid-season white seedless grape is being introduced for commercial production. Valley Pearl will provide growers and consumers with a large white seedless grape that is productive with spur pruning.

Technical Abstract: Large quantities of fungicides are being use to control powdery mildew, which is the most important fungal disease in grape growing regions of the world. Without these fungicides, over 95% of the crop could be lost. Repeated use of sterol biosynthesis inhibitor and strobilurin-type fungicides can lead to fungicide resistant PM strains. Genetically resistant grapes will provide an alternative to fungicide sprays. Many sources of resistance have been used to develop powdery mildew resistant germplasm. Molecular markers have been developed which aid the selection of individuals with more than one source of resistance. In 2011, 20 table grape seedlings were selected for PM resistance and fruit quality and propagated into 2 vine production plots. One red seedless selection also will be tested in a 27 vine production plot. A white resistant selection will fruit in a 27 vine production plot in 2012 and has very good eating quality, small aborted seeds and good production. Valley Pearl, a new early to mid-season white seedless grape is being introduced for commercial production. Valley Pearl was tested in the San Joaquin Valley and Coachella Valley. Valley Pearl will provide growers and consumers a large white seedless grape that is productive with spur pruning.

Last Modified: 11/25/2014
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